Control of machines, such as excavators and material handlers, can be a complex task requiring a significant amount of skill on the part of an operator and typically requires manipulation of multiple input devices such as joysticks. An example may be the movement of a work tool, such as a bucket, along a desired path in a consistent, controlled manner from a first location, such as a dig location, to a second location, such as a dump location. Upon reaching the dump location, the operator will typically operate the input devices to slow down the movement of the work tool in order to accurately position the work tool and, in the case of a bucket, minimize any spillage from the bucket until it is in its desired dump location.
One example of a machine that includes automated control over a portion of movement of a work tool is disclosed in U.S. Pat. No. 5,968,104 (the '104 patent) issued to Egawa, et al. on Oct. 19, 1999. In particular, the '104 patent discloses a hydraulic excavator having an area limiting excavation control system. The area limiting excavation control system has a setting device permitting an operator to set an excavation area at which an end of a bucket is allowed to move. The area limiting excavation control system also includes angle sensors disposed at pivot points of a boom, an arm, and a bucket for detecting respective rotational angles and velocities thereof, a tilt angle sensor for detecting a tilt angle of the excavator's body in a back-and-forth direction (fore/aft direction), and a pressure sensor for detecting a load pressure of the boom as it is moved upward in response to signals generated by a control lever.
The excavation control system limits the speed of the bucket based on changing machine parameters. Specifically, as the bucket nears a boundary of the operator set excavation area during a fore/aft or up/down movement operation (i.e., during a digging operation), the speed of the bucket is slowed in the direction of the boundary such that the bucket stops at the boundary of the excavation area without exiting the desired excavation area. Stopping of the bucket is controlled by adapting flow rate characteristics of control valves associated with movement of the bucket based upon changing machine parameters such as speed, load, position, posture, and temperature. Although the area limiting control system of the '104 patent may improve operator control and machine performance of a hydraulic excavator under some conditions, its system does not provide a full and efficient solution to certain challenges facing the machine operator.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein nor to limit or expand the prior art discussed. Thus the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use within the innovations described herein, nor is it intended to indicate any element, including solving the motivating problem, to be essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.